Three Dimensional LIDAR System With Targeted Field of View

ABSTRACT

A plurality of beams of illumination light are emitted from a LIDAR device over a range of angles and scanned about an axis of rotation. The range of angles includes the axis of rotation. Intermediate electronics boards provide mechanical support and electrical connectivity between a rotating electronics board and various elements of a light emission and collection engine. One or more of the optical elements of the collection optics, the illumination optics, or both, is constructed from one or more materials that absorb light outside of a predetermined wavelength range. An overmolded lens is fixedly coupled to one or more of the light detecting elements to collect incoming light over a larger range of angles. A lens element is disposed in the light path between a light emitting element and the illumination optics to flatten the intensity distribution of light emitted from the light emitting element to reduce peak intensity.

CROSS REFERENCE TO RELATED APPLICATION

The present application for patent claims priority under 35 U.S.C. §119from U.S. provisional patent application Ser. No. 62/260,205, entitled“Three Dimensional LIDAR System With Targeted Field of View,” filed Nov.25, 2015, the subject matter of which is incorporated herein byreference in its entirety.

TECHNICAL FIELD

The described embodiments relate to three dimensional LIDAR systems.

BACKGROUND INFORMATION

LIDAR systems employ pulses of light to measure distance to an objectbased on the time of flight (TOF) of the pulsed of light. A pulse oflight emitted from a light source of the LIDAR system interacts with adistal object. A portion of the light reflects from the object andreturns to a detector of the LIDAR system. Based on the time elapsedbetween emission of the pulse of light and detection of the returnedpulse of light, a distance is estimated.

In some examples, a pulsed laser emitter is employed to generated lightpulses. The light pulses are focused through a lens or lens assembly.The time it takes for that pulse of light to return to a detectormounted near the emitter is measured. A distance is derived from thetime measurement with high accuracy.

In some examples, multiple pulses are emitted in rapid succession, andthe direction of those emissions is sequentially varied. In theseexamples, each distance measurement can be considered a pixel, and acollection of pixels emitted and captured in rapid succession (i.e.,“point cloud”) can be rendered as an image or analyzed for other reasons(e.g., detecting obstacles). In some examples, viewing software isemployed to render the resulting point clouds as images that appearthree dimensional to a user. Different schemes can be used to depict thedistance measurements as 3-D images that appear as if they were capturedby a live action camera.

Some LIDAR systems employ a single laser emitter/detector combinationcombined with a rotating mirror to effectively scan across a plane.Distance measurements performed by such a system are effectively twodimensional (i.e., planar), and the captured distance points arerendered as a 2-D (i.e. single plane) point cloud.

In some examples, rotating mirrors are rotated at very fast speeds—inthe thousands of RPMs. As stated above, this design inherently rendersonly a 2-D point cloud. However, a 3-D point cloud is often required.The other dimension is provided for in a number of ways. Most often, theentire instrument is actuated up and down and/or back and forth, oftenon a gimbal—a process known within the art as winking or nodding thesensor. Thus, a single beam lidar unit can be employed to capture anentire 3-D array of distance points, albeit one point at a time. In arelated example, a prism is employed to “divide” the laser pulse intomultiple layers, each having a slightly different vertical angle. Thissimulates the nodding effect described above, but without actuation ofthe sensor itself.

In all the above examples, the main premise is a single laseremitter/detector combination, where the light path is somehow altered toachieve a broader field of view than a single sensor. The device isinherently limited to the number of pixels it can generate due to thelimitation of how many pulses per second are possible from a singlelaser. Any alteration of the beam path, whether it is by mirror, prism,or actuation of the device, causes the point cloud to be less dense, butcover a broader area.

As noted above, 3-D point cloud systems exist in several configurations.However, in many applications it is necessary to see over a broad fieldof view. For example, in an autonomous vehicle application, the verticalfield of view should extend above the horizon, in case the car enters adip in the road, and should extend down as close as possible to see theground in front of the vehicle. In addition, it is necessary to have aminimum of delay between the actions happening in the real world and theimaging of those actions. In some examples, it is desirable to provide acomplete image update at least five times per second.

Improvements in field of view and the point cloud density of 3-D imagingsystems are desired.

SUMMARY

Methods and systems for performing LIDAR measurements are presentedherein. In one aspect, a plurality of beams of illumination light from aLIDAR device are emitted into a three dimensional environment over arange of angles. The range of angles includes the axis of rotation of alight emission and collection engine of the LIDAR device. The lightemission and collection engine include a plurality of light emittingelements, light detecting elements, illumination optics and collectionoptics.

In a further aspect, the LIDAR device is configured to scan each of theplurality of beams of light about the axis of rotation. In this manner,each beam of light projected into the environment traces a cone shapedpattern.

In yet another aspect, the light emission and collection engine includesintermediate electronics boards that provide mechanical support andelectrical connectivity between a rotating electronics board and variouselements of the light emission and collection engine. The intermediateelectronics boards are each coupled to the rotating electronics boardsuch that the planar surface of each of the intermediate electronicsboards is oriented perpendicular to the planar surface of the rotatingelectronics board.

In yet another aspect, one or more of the optical elements of thecollection optics, the illumination optics, or both is constructed fromone or more materials that absorb light outside of a predeterminedwavelength range that includes the wavelengths of light emitted by eachof the light emitting elements.

In yet another aspect, an overmolded lens is fixedly coupled to one ormore of the light detecting elements. The overmolded lens protects thelight detecting element and is shaped to collect incoming light over alarger range of angles than would be possible without the lens.

In yet another aspect, a lens element is disposed in the light pathbetween a light emitting element and the illumination optics to flattenthe intensity distribution of light emitted from the light emittingelement. This reduces the peak intensity of light emitted from the LIDARsystem.

The foregoing is a summary and thus contains, by necessity,simplifications, generalizations and omissions of detail; consequently,those skilled in the art will appreciate that the summary isillustrative only and is not limiting in any way. Other aspects,inventive features, and advantages of the devices and/or processesdescribed herein will become apparent in the non-limiting detaileddescription set forth herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified diagram illustrative of one embodiment of a 3-DLIDAR system 100 in at least one novel aspect.

FIG. 2 depicts an exploded view of 3-D LIDAR system 100 in one exemplaryembodiment.

FIG. 3 depicts a view of light emission and collection engine 112 of 3-DLIDAR system 100.

FIG. 4 depicts a view of collection optics 116 of 3-D LIDAR system 100in greater detail.

FIG. 5 depicts a cutaway view of collection optics 116 of 3-D LIDARsystem 100 that illustrates the shaping of each beam of collected light118.

FIG. 6 depicts an illustration of one exemplary embodiment of anindividual element 113A of the array of light detecting elements 113depicted in FIG. 2.

FIG. 7 depicts an illustration of one exemplary embodiment of anindividual element 114A of the array of light emitting elements 114depicted in FIG. 2.

FIG. 8 depicts elements of a 3-D LIDAR system including a pulseillumination system 130, a light detection system 150, and controller140.

FIG. 9 depicts an illustration of the timing of emission of a pulsemeasurement beam and capture of the returning measurement pulse.

FIG. 10 depicts an illustration of the timing of light emission fromsixteen pulse illumination sub-systems.

FIG. 11 depicts a flowchart illustrative of a method 200 of performingLIDAR measurements in at least one novel aspect.

DETAILED DESCRIPTION

Reference will now be made in detail to background examples and someembodiments of the invention, examples of which are illustrated in theaccompanying drawings.

FIG. 1 is a diagram illustrative of an embodiment of a 3-D LIDAR system100 in one exemplary operational scenario. 3-D LIDAR system 100 includesa lower housing 101 and an upper housing 102. Lower housing 101 includesa frame structure configured to be attached to an object that is thereference from which LIDAR measurements are made (e.g., a vehicle, atower, an aircraft, etc.). Upper housing 102 includes a domed shellelement 103 constructed from a material that is transparent to infraredlight (e.g., light having a wavelength within the spectral range of 700to 1,700 nanometers). In one example, domed shell element 103 istransparent to light having a narrow range of wavelengths centered at905 nanometers.

As depicted in FIG. 1, a plurality of beams of light 105 are emittedfrom 3-D LIDAR system 100 through domed shell element 103 over anangular range, α, measured from a central axis of rotation 104. In oneaspect, the plurality of beams of light 105 spans the angular range fromthe central axis of rotation 104 to the angle, α, measured from centralaxis of rotation 104. In this sense, each beam of illumination light isemitted from the LIDAR device at a different angle with respect to thecentral axis of rotation, and one or more of the beams of light 105 areparallel to or nearly parallel to the central axis of rotation 104.

In the embodiment depicted in FIG. 1, each beam of light is projectedonto a plane defined by the x and y axes at a plurality of differentlocations spaced apart from one another. For example, beam 106 isprojected onto the xy plane at location 107. Thus, each beam ofillumination light emitted from the light emission and collection engineilluminates a different spot of a three dimensional environment with ameasurement pulse of illumination light.

In a further aspect, 3-D LIDAR system 100 is configured to scan each ofthe plurality of beams of light 105 about the central axis of rotation104. In the embodiment depicted in FIG. 1, each beam of light projectedonto the xy plane traces a circular pattern centered about theintersection point of the central axis of rotation 104 and the xy plane.For example, over time, beam 106 projected onto the xy plane traces outa circular trajectory 108 centered about central axis of rotation 104.The xy plane is depicted in FIG. 1 to illustrate the spatial separationof beams emitted from 3-D LIDAR system 100. In general, the beamsemitted from 3-D LIDAR system 100 are projected into the surroundingenvironment and are incident on objects in the path of each respectivebeam.

FIG. 2 depicts an exploded view of 3-D LIDAR system 100 in one exemplaryembodiment. 3-D LIDAR system 100 further includes a light emission andcollection engine 112 that rotates about central axis of rotation 104.In another aspect, a central optical axis 117 of light emission andcollection engine 112 (e.g., middle of angular range, α, of beams ofillumination light 105 emitted from LIDAR device 100) is tilted at anangle, β, with respect to central axis of rotation 104. In general,angle, β, can be any angle between zero degrees and α/2.

As depicted in FIG. 2, 3-D LIDAR system 100 includes a stationaryelectronics board 110 mounted in a fixed position with respect to lowerhousing 101. Rotating electronics board 111 is disposed above stationaryelectronics board 110 and is configured to rotate with respect tostationary electronics board 110 at a predetermined rotational velocity(e.g., more than 200 revolutions per minute), along with the lightemission and collection engine 112. Electrical power signals andelectronic signals are communicated between stationary electronics board110 and rotating electronics board 111 over one or more transformer,capacitive or optical elements, resulting in a contactless transmissionof these signals. Light emission and collection engine 112 is fixedlypositioned with respect to the rotating electronics board 111, and thusrotates about central axis of rotation 104 at the predetermined angularvelocity, ω. The planar surface of rotating electronics board 111 isoriented perpendicular to the central axis of rotation 104.

As depicted in FIG. 2, light emission and collection engine 112 includesan array of light emitting elements 114 and an array of light detectingelements 113. Light emitted from each of the light emitting elements 114is directed toward a mirror (not shown). Light reflected from the mirrorpasses through a series of illumination optics 115 that approximatelycollimate the emitted light into an array of beams of illumination light105 that are emitted from 3-D LIDAR system 100 as depicted in FIG. 1.

In general, any number of light emitting elements can be arranged tosimultaneously emit any number of light beams from 3-D LIDAR system 100.In addition, any number of light emitting elements can be arranged tosequentially emit any number of light beams from 3-D LIDAR system 100.In one embodiment, two or more light emitting elements are triggered toemit light substantially simultaneously, and then after a programmedperiod of time has elapsed, another two or more light emitting elementsare triggered to emit light substantially simultaneously.

Light reflected from objects in the environment is collected bycollection optics 116. Collected light passes through collection optics116 where it is focused onto each detecting element of the array ofdetecting elements 113. Nominally, each light detecting elementcorresponds to a different light emitting element. After passing throughcollection optics 116, the collected light is reflected from a mirror(not shown) onto each detector element. In practice, crosstalk amongeach measurement channel limits the number of channels that can betriggered simultaneously. However, to maximize imaging resolution, it isdesirable to trigger as many channels as possible, simultaneously, sothat time of flight measurements are obtained from many channels at thesame time, rather than sequentially.

FIG. 3 depicts another view of light emission and collection engine 112.In yet another aspect, light emission and collection engine 112 includesintermediate electronics boards 121, 122, and 123 which providemechanical support and electrical connectivity between rotatingelectronics board 111 and various elements of light emission andcollection engine 112. For example, each of the array of light detectingelements 113 is mounted to intermediate electronics board 121.Intermediate electronics board 121, in turn, is mechanically andelectrically coupled to rotating electronics board 111. Similarly, eachof the array of light emitting elements 114 is mounted to intermediateelectronics board 123. Intermediate electronics board 123, in turn, ismechanically and electrically coupled to rotating electronics board 111.In another example, illumination optics 115 and collection optics 116are mechanically mounted to intermediate electronics board 122. In thisexample, intermediate electronics board 122 spatially separates andoptically obscures the illumination optics 115 from the collectionoptics 116 to avoid contamination of the collected light withillumination light. Intermediate electronics board 122, in turn, ismechanically and electrically coupled to rotating electronics board 111.In this manner, the intermediate electronics boards provide mechanicaland electrical connectivity and additional board area for mountingelectrical components required for the operation of 3-D LIDAR system100. The intermediate electronics boards are each coupled to therotating electronics board 111 such that the planar surface of each ofthe intermediate electronics boards is oriented perpendicular to theplanar surface of the rotating electronics board.

FIG. 4 depicts a view of collection optics 116 in greater detail. Asdepicted in FIG. 4, collection optics 116 include four lens elements116A-D arranged to focus collected light 118 onto each of the array ofdetecting elements 113. Light passing through collection optics 116 isreflected from mirror 124 and is directed onto each of the array ofdetecting elements 113.

In another aspect, one or more of the optical elements of collectionoptics 116 is constructed from one or more materials that absorb lightoutside of a predetermined wavelength range that includes thewavelengths of light emitted by each of the array of light emittingelements 114. In one example, one or more of the lens elements areconstructed from a plastic material that includes a colorant additive toabsorb at least fifty percent of light having wavelengths less thaninfrared light generated by each of the array of light emitting elements114. In another example, the plastic material absorbs at least ninetypercent of light having wavelengths less than the infrared lightgenerated by each of the array of light emitting elements 114. In oneexample, the colorant is Epolight 7276A available from Aako BV (TheNetherlands). In general, any number of different colorants can be addedto any of the plastic lens elements of collection optics 116 to filterout undesired spectra.

FIG. 5 depicts a cutaway view of collection optics 116 to illustrate theshaping of each beam of collected light 118.

As described hereinbefore, one or more of the optical elements ofcollection optics 116 is constructed from one or more materials thatabsorb light outside of a predetermined wavelength range that includesthe wavelengths of light emitted by each of the array of light emittingelements 114. However, in general, one or more of the optical elementsof illumination optics 115 may also be constructed from one or morematerials that absorb light outside of a predetermined wavelength rangethat includes the wavelengths of light emitted by each of the array oflight emitting elements 114.

FIG. 6 depicts an illustration of one exemplary embodiment of anindividual element 113A of the array of light detecting elements 113depicted in FIG. 2. Detecting element 113A includes an electronics board130 upon which a light detecting element 131 is mounted. In someembodiments, light detecting element 131 is an avalanche photodiode(APD) element. However, in general, any suitable light detecting elementmay be employed.

In yet another aspect, an overmolded lens 132 is fixedly coupled to thelight detecting element. The overmolded, lens protects the lightdetecting element and is shaped to collect incoming light over a largerrange of angles than would be possible without the lens. In someexamples, overmolded lens 132 is a domed lens. In some other examples,overmolded lens 132 is shaped as a compound parabolic concentrator(CPC).

FIG. 7 depicts an illustration of one exemplary embodiment of anindividual element 114A of the array of light emitting elements 114depicted in FIG. 2. Emitting element 114A includes an electronics board140 upon which a light emitting element 141 is mounted. In someembodiments, light emitting element 141 is a diode laser element.However, in general, any suitable light source may be employed.

In yet another aspect, a lens element is disposed in the light pathbetween light emitting element 141 and illumination optics 114 toflatten the intensity distribution of light emitted from light emittingelement 141. In general, a laser diode based light emitting elementemits light having a Gaussian intensity distribution. However, 3-D LIDARsystem 100 is typically operated in an unstructured environment thatincludes humans with limited tolerance for infrared light intensitybefore eye damage may result. To ensure that the emission intensity of3-D LIDAR system 100 remains below acceptable limits without attenuatingthe amount of total photonic flux, lens element 142 flattens theGaussian distribution and thus reduces the peak intensity of lightemitted from 3-D LIDAR system 100. In some examples, lens element 142 isa diffractive optical element configured to transform a Gaussiandistribution to a flat-top distribution. However, in general, anyoptical element configured to flatten the Gaussian distribution may becontemplated.

The light emitting elements of 3-D LIDAR system 100 are pulseillumination sources, each emitting a pulsed beam of illumination lightfrom the LIDAR device into the surrounding environment. In someembodiments, the light emitting elements are laser based. In someembodiments, the light emitting elements are based on one or more lightemitting diodes. In general, any suitable pulsed illumination source maybe contemplated.

Each measurement beam illuminates a particular location of the threedimensional environment (e.g., pixel) with a measurement pulse ofillumination light. Each measurement pulse interrogates one location inthe surrounding environment and results in an estimate of distancebetween the 3-D LIDAR system and the location. Light reflected from thelocation is detected by a corresponding light detecting element of theLIDAR system during a measurement window. The light detecting elementdetects the measurement pulse reflected from a particular location inthe surrounding three dimensional environment. In this manner, thereflection from a particular measurement location of each measurementpulse is captured by the LIDAR system.

In a further aspect, the LIDAR system determines the time of flight ofthe measurement pulse from the LIDAR device to the particularilluminated spot of the three dimensional environment and back to theLIDAR device. The time of flight is determined based on the reflectedlight detected during the measurement window. The distance between theLIDAR device and the particular location of the three dimensionalenvironment illuminated by the measurement pulse is determined based onthe time of flight and the known speed of light.

FIG. 8 depicts elements of a LIDAR system including a pulse illuminationsystem 130, a pulse light detection system 150, and controller 140 inone embodiment. The embodiment depicted in FIG. 8 is provided by way ofnon-limiting example, and many other suitable embodiments for performingpulse LIDAR measurements as described herein may be contemplated withinthe scope of this patent document.

Pulse illumination system 130 includes a pulsed light emitting element137. Pulsed light emitting element 137 generates pulsed light emissionin response to a pulsed electrical signal 136 provided to the pulsedlight emitting element. The light generated by pulsed light emittingelement 137 is focused and projected onto a particular location 138 inthe surrounding environment by one or more optical elements of the LIDARsystem. In one example, light emitted by pulsed light emitting element137 is focused and projected onto a particular location by illuminationoptics 115 that collimate the emitted light into a pulsed beam of light106 emitted from 3-D LIDAR system 100 as depicted in FIG. 1.

Pulse illumination system 130 includes one or more electrical energystorage elements (ESE) selectively coupled to the pulsed light emittingelement 137. For illustration purposes, FIG. 8 depicts one energystorage element (labeled ESE 132), however, in general any number ofenergy storage elements may be employed to generate the a pulse ofillumination light. In some examples, each energy storage element is acapacitor. An electrical energy source 131 (e.g., a voltage source) iselectrically coupled to each of the energy storage elements and provideselectrical energy to each of electrical energy storage elements. Each ofthe electrical energy storage elements is selectively coupled to thepulsed light emitting device 137 by a switching element. Again, forillustration purposes, FIG. 8 depicts one switching element (labeled139). Each switching element is configured to toggle between two statesdepending on the state of a control signal (e.g., digital controlsignal, PC). In a first state, a switching element is substantiallynon-conductive. In this state, a corresponding energy storage element iseffectively disconnected from the pulsed light emitting element 137. Inthis state, electrical energy flows from the electrical energy source131 to each corresponding energy storage element to effectively chargethe energy storage element. In a second state, the switching element issubstantially conductive. In this state, the corresponding energystorage element is electrically coupled to the pulsed light emittingelement 137. In this state, electrical energy flows from the energystorage element to the pulsed light emitting element 137.

As depicted in FIG. 8, any electrical current simultaneously supplied tothe pulsed light emitting element 137 by any of the energy storageelements is effectively additive. In this manner, the electrical currentsignal 136 provided to the pulsed light emitting element 137 iseffectively shaped by control signal, PC. For example, when PC controlsswitching element 139 to toggle from a substantially non-conductivestate to a substantially conductive state, a pulse of electrical current136 is provided to pulsed light emitting device 137. Similarly, pulsesof electrical current can be provided to pulsed light emitting device137 from other energy storage elements at the same time.

As depicted in FIG. 8, controller 140 generates control signal, PC,which controls the timing of electrical current pulses provided topulsed light emitting element 137, and thus, the timing of pulses oflight emitted from the LIDAR device.

In general, each pulse commanded by controller 140 can vary in magnitudeand duration. Furthermore, the delay between pulses can also be varied.

In general, a pulse illumination system 130 may include any number ofelectrical energy storage elements selectively coupled to a pulsed lightemitting element. Furthermore, one or more of the electrical energystorage elements may have an energy storage capacity that differs fromone or more of the other electrical energy storage elements.

In a further embodiment, a LIDAR system, such as LIDAR system 100depicted in FIG. 1, includes sixteen pulse illumination systemsoperating in coordination with a common controller (e.g., controller140). FIG. 10 depicts an exemplary diagram 180 illustrating the timingof light emission from each of the sixteen pulse illumination systems.

As depicted in FIG. 10, a measurement pulse is emitted from a firstpulse illumination system. After a delay time, T_(DELAY), a measurementpulse is emitted from a second pulse illumination system of the LIDARdevice. In this manner a sequence of sixteen measurement pulses areemitted in different directions from the LIDAR device during ameasurement period, T_(MEASUREMENT). The energy storage elements of eachof the sixteen pulse illumination systems are charged after themeasurement period for a charging period, T_(CHARGE). After, thecharging period, another measurement pulse is emitted from each pulseillumination system over a subsequent measurement period.

In some embodiments, the delay time, T_(DELAY), is set to be greaterthan the time of flight of the measurement pulse to and from an objectlocated at the maximum range of the LIDAR device. In this manner, thereis no cross-talk among any of the sixteen pulse illumination systems.

In some other embodiments, a measurement pulse may be emitted from onepulse illumination system before a measurement pulse emitted fromanother pulse illumination system has had time to return to the LIDARdevice. In some of these embodiments, care is taken to ensure that thereis sufficient spatial separation between the areas of the surroundingenvironment interrogated by each beam to avoid cross-talk.

As depicted in FIG. 8, light reflected from location 138 is detected bylight detecting element 155. Light detecting element 155 generates anoutput signal 151 that is amplified by an analog trans-impedanceamplifier 152. In general, the amplification of output signal 151 mayinclude multiple, amplifier stages. In this sense, analogtrans-impedance amplifier 152 is provided by way of non-limitingexample, as many other analog signal amplification schemes may becontemplated within the scope of this patent document.

The amplified signal 153 is communicated to controller 140. Ananalog-to-digital converter (ADC) 144 of controller 140 is employed toconvert the analog signal 153 into a digital signal used for furtherprocessing. Controller 140 generates an enable/disable signal 145employed to control the timing of data acquisition by ADC 144 in concertwith pulse control signal, PC.

FIG. 9 depicts an illustration of the timing associated with theemission of a measurement pulse and capture of the returning measurementpulse. As depicted in FIG. 9, the measurement begins with a pulse firingsignal 161 (e.g., PC) generated by controller 140. Due to internalsystem delay, an index signal 162 is determined that is shifted from thepulse firing signal 161 by a time delay, T_(D). The time delay includesthe known delays associated with emitting light from the LIDAR system(e.g., signal communication delays and latency associated with theswitching elements, energy storage elements, and pulsed light emittingdevice) and known delays associated with collecting light and generatingsignals indicative of the collected light (e.g., amplifier latency,analog-digital conversion delay, etc.). The index signal is generated asa way to measure time delay within the system. As such, the index signalmay be regenerated at any suitable time during system operation. Inaddition, an index signal may be employed to estimate time delayassociated with one or more measurement channels.

As depicted in FIG. 9, a return signal 163 is detected by the LIDARsystem in response to the illumination of a particular location. Ameasurement window (i.e., a period of time over which collected returnsignal data is associated with a particular measurement pulse) isinitiated by enabling data acquisition from light detecting element 150.Controller 140 controls the timing of the measurement window tocorrespond with the window of time when a return signal is expected inresponse to the emission of a measurement pulse. In some examples, themeasurement window is enabled at the point in time when the measurementpulse is emitted and is disabled at a time corresponding to the time offlight of light over a distance that is twice the range of the LIDARsystem. In this manner, the measurement window is open to collect returnlight from objects adjacent to the LIDAR system (i.e., negligible timeof flight) to objects that are located at the maximum range of the LIDARsystem. In this manner, all other light that cannot possibly contributeto useful return signal is rejected.

As depicted in FIG. 9, return signal 163 includes two return measurementpulses that correspond with the emitted measurement pulse. In general,signal detection is performed on all detected measurement pulses.Further signal analysis may be performed to identify the closest signal(e.g., first instance of the return measurement pulse), the strongestsignal, and the furthest signal (e.g., last instance of the returnmeasurement pulse in the measurement window). Any of these instances maybe reported as potentially valid distance measurements by the LIDARsystem. For example, a time of flight, TOF₁, may be calculated from theclosest (i.e., earliest) return measurement pulse that corresponds withthe emitted measurement pulse as depicted in FIG. 9.

FIG. 11 illustrates a method 200 of performing LIDAR measurements in atleast one novel aspect. Method 200 is suitable for implementation by aLIDAR system such as LIDAR system 100 illustrated in FIG. 1 of thepresent invention. In one aspect, it is recognized that data processingblocks of method 200 may be carried out via a pre-programmed algorithmexecuted by one or more processors of controller 140, or any othergeneral purpose computing system. It is recognized herein that theparticular structural aspects of LIDAR system 100 do not representlimitations and should be interpreted as illustrative only.

In block 201, a plurality of beams of illumination light are emittedfrom a LIDAR device into a three dimensional environment over a range ofangles that includes an axis of rotation of a plurality of lightemitting elements of the LIDAR device. The plurality of beams ofillumination light each illuminate a different spot of the threedimensional environment with a measurement pulse of illumination light.

In block 202, the plurality of measurement pulses reflected from eachdifferent spot of the three dimensional environment illuminated by theplurality of beams of illumination light are detected.

In block 203, a plurality of output signals are generated; eachindicative of one of the plurality of reflected measurement pulses.

In block 204, each of the plurality of output signals are converted to adigital signal.

In block 205, a time of flight of each measurement pulse from the LIDARdevice to each particular spot of the three dimensional environment andback to the LIDAR device is determined based on each of the digitalsignals.

In one or more exemplary embodiments, the functions described may beimplemented in hardware, software, firmware, or any combination thereof.If implemented in software, the functions may be stored on ortransmitted over as one or more in or code on a computer-readablemedium. Computer-readable media includes both computer storage media andcommunication media including any medium that facilitates transfer of acomputer program from one place to another. A storage media may be anyavailable media that can be accessed by a general purpose or specialpurpose computer. By way of example, and not limitation, suchcomputer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or otheroptical disk storage, magnetic disk storage or other magnetic storagedevices, or any other medium that can be used to carry or store desiredprogram code means in the form of instructions or data structures andthat can be accessed by a general-purpose or special-purpose computer,or a general-purpose or special-purpose processor. Also, any connectionis properly termed a computer-readable medium. For example, if thesoftware is transmitted from a website, server, or other remote sourceusing a. coaxial cable, fiber optic cable, twisted pair, digitalsubscriber line (DSL), or wireless technologies such as infrared, radio,and microwave, then the coaxial cable, fiber optic cable, twisted pair,DSL, or wireless technologies such as infrared, radio, and microwave areincluded in the definition of medium. Disk and disc, as used herein,includes compact disc (CD), laser disc, optical disc, digital versatiledisc (DVD), floppy disk and blu-ray disc where disks usually reproducedata magnetically, while discs reproduce data optically with lasers.Combinations of the above should also be included within the scope ofcomputer-readable media.

Although certain specific embodiments are described above forinstructional purposes, the teachings of this patent document havegeneral applicability and are not limited to the specific embodimentsdescribed above. Accordingly, various modifications, adaptations, andcombinations of various features of the described embodiments can bepracticed without departing from the scope of the invention as set forthin the claims.

What is claimed is:
 1. A light detection and ranging (LIDAR) device,comprising: a light emission and collection engine configured to rotateabout an axis of rotation, the light emission and collection engineincluding, a plurality of light emitting elements each emitting a beamof illumination light from the LIDAR device at a different angle withrespect to the axis of rotation, wherein at least one of the pluralityof light emitting elements is configured to emit a beam of illuminationlight that is parallel or nearly parallel with the axis of rotation,wherein each beam of illumination light emitted from the light emissionand collection engine illuminates a different spot of a threedimensional environment with a measurement pulse of illumination light;a plurality of light detecting elements each corresponding to one of theplurality of light emitting elements, wherein each of the plurality oflight detecting elements detects an amount of the measurement pulsereflected from each different spot of the three dimensional environmentilluminated by each corresponding beam of illumination light andgenerates an output signal indicative of the detected amount of light;and a computing system configured to: receive the output signalindicative of the detected amount of light; convert the output signal toa digital signal; and determine a time of flight of the measurementpulse from the LIDAR device to the particular spot of the threedimensional environment and back to the LIDAR device based on thedigital signal.
 2. The LIDAR device of claim 1, further comprising: ahousing fixable to an object from which LIDAR measurements are made; astationary electronics board mechanically coupled to the housing; arotating electronics board having a planar surface arrangedperpendicular to the axis of rotation, wherein the rotating electronicsboard rotates with the light emission and collection engine, and whereinelectrical power and electronic signals are communicated between thestationary electronics board and the rotating electronics board; and twoor more intermediate electronics boards each coupled to the rotatingelectronics board such that a planar surface of each of the intermediateelectronics boards is oriented perpendicular to the planar surface ofthe rotating electronics board, wherein the two or more intermediateelectronics boards are mechanically and electrically coupled to thelight emission and collection engine.
 3. The LIDAR device of claim 2,wherein a first of the two or more intermediate electronics boards ismechanically and electrically coupled to each of the plurality of lightemitting elements, and wherein a second of the two or more intermediateelectronics boards is mechanically and electrically coupled to each ofthe plurality of light detecting elements.
 4. The LIDAR device of claim2, wherein a third of the two or more intermediate electronics boards ismechanically coupled to one or more lens elements of an illuminationoptics subsystem of the LIDAR device and one or more lens elements of acollection optics subsystem of the LIDAR device, wherein the thirdintermediate electronics board spatially separates and opticallyobscures the illumination optics subsystem from the collection opticssubsystem.
 5. The LIDAR device of claim 1, further comprising: anillumination optics subsystem configured to collimate the beams of lightemitted from the plurality of light emitting elements; and a collectionoptics subsystem configured to focus the collected light onto eachrespective light detecting element of the plurality of light detectingelements.
 6. The LIDAR device of claim 5, wherein one or more of theoptical elements of the collection optics subsystem is constructed fromone or more materials that absorb at least fifty percent of lightoutside of a predetermined wavelength range, wherein the predeterminedwavelength range includes the wavelengths of light emitted by each ofthe plurality of light emitting elements.
 7. The LIDAR device of claim5, wherein one or more lens elements of the illumination opticssubsystem are configured to flatten an intensity distribution of lightemitted from each of the plurality of light emitting elements.
 8. TheLIDAR device of claim 7, wherein the one or more lens elements includesa diffractive optical element.
 9. The LIDAR device of claim 1, furthercomprising: a plurality of overmolded lenses each fixedly coupled to oneof the plurality of light detecting elements.
 10. The LIDAR device ofclaim 9, wherein one or more of the plurality of overmolded lenses is adomed lens or a compound parabolic concentrator (CPC).
 11. The LIDARdevice of claim 1, wherein two or more of the plurality of lightemitting elements are configured to emit light simultaneously.
 12. TheLIDAR device of claim 1, wherein two or more of the plurality of lightemitting elements are configured to emit light sequentially.
 13. TheLIDAR device of claim 4, wherein a first group of two or more of theplurality of light emitting elements are triggered to emit lightsubstantially simultaneously, and, after a programmed period of time haselapsed, a second group of two or more of the plurality of lightemitting elements are triggered to emit light substantiallysimultaneously.
 14. A light detection and ranging (LIDAR) device,comprising: a light emission and collection engine configured to rotateabout an axis of rotation, the light emission and collection engineincluding, a plurality of light emitting elements each emitting a beamof illumination light from the LIDAR device at a different angle withrespect to the axis of rotation, wherein at least one of the pluralityof light emitting elements is configured to emit a beam of illuminationlight that is parallel or nearly parallel with the axis of rotation,wherein each beam of illumination light emitted from the light emissionand collection engine illuminates a different spot of a threedimensional environment with a measurement pulse of illumination light;a plurality of light detecting elements each corresponding to one of theplurality of light emitting elements, wherein each of the plurality oflight detecting elements detects an amount of the measurement pulsereflected from each different spot of the three dimensional environmentilluminated by each corresponding beam of illumination light andgenerates an output signal indicative of the detected amount of light; arotating electronics board having a planar surface arrangedperpendicular to the axis of rotation, wherein the rotating electronicsboard rotates with the light emission and collection engine; and two ormore intermediate electronics boards each coupled to the rotatingelectronics board such that a planar surface of each of the intermediateelectronics boards is oriented perpendicular to the planar surface ofthe rotating electronics board, wherein the two or more intermediateelectronics boards are mechanically and electrically coupled to thelight emission and collection engine.
 15. The LIDAR device of claim 14,wherein a first of the two or more intermediate electronics boards ismechanically and electrically coupled to each of the plurality of lightemitting elements, and wherein a second of the two or more intermediateelectronics boards is mechanically and electrically coupled to each ofthe plurality of light detecting elements.
 16. The LIDAR device of claim14, wherein a third of the two or more intermediate electronics boardsis mechanically coupled to one or more lens elements of an illuminationoptics subsystem of the LIDAR device and one or more lens elements of acollection optics subsystem of the LIDAR device, wherein the thirdintermediate electronics board spatially separates and opticallyobscures the illumination optics subsystem from the collection opticssubsystem.
 17. The LIDAR device of claim 14, further comprising: acollection optics subsystem configured to focus the collected light ontoeach respective light detecting element of the plurality of lightdetecting elements, wherein one or more of the optical elements of thecollection optics subsystem is constructed from one or more materialsthat absorb at least fifty percent of light outside of a predeterminedwavelength range, wherein the predetermined wavelength range includesthe wavelengths of light emitted by each of the plurality of lightemitting elements.
 18. The LIDAR device of claim 14, further comprising:an illumination optics subsystem configured to collimate the beams oflight emitted from the plurality of light emitting elements, wherein oneor more lens elements of the illumination optics subsystem areconfigured to flatten an intensity distribution of light emitted fromeach of the plurality of light emitting elements.
 19. A methodcomprising: emitting a plurality of beams of illumination light from aLIDAR device into a three dimensional environment over a range of anglesthat includes an axis of rotation of a plurality of light emittingelements of the LIDAR device, the plurality of beams of illuminationlight each illuminate a different spot of the three dimensionalenvironment with a measurement pulse of illumination light; detectingthe plurality of measurement pulses reflected from each different spotof the three dimensional environment illuminated by the plurality ofbeams of illumination light; generating a plurality of output signalseach indicative of one of the plurality of reflected measurement pulses;converting each of the plurality of output signals to a digital signal;and determining a time of flight of each measurement pulse from theLIDAR device to each particular spot of the three dimensionalenvironment and back to the LIDAR device based on each of the digitalsignals.
 20. The method of claim 19, further comprising: flattening anintensity distribution of light emitted from each of the plurality oflight emitting elements.